Commonly known assemblies for downward driving of pier sections, and for lifting of building foundations upon the driven pier sections incorporate and utilize a conically bored drawing sleeve and wedge shaped collet shoes assembly (i.e., a collet clamp) for substantially annularly clamping a foundation support pier. Such collet clamp allows hydraulic cylinder actuated machinery to drive the pier downwardly into the earth at a building's foundation, and thereafter, upon placement of the pier, to upwardly draw and lift the building's foundation along such pier for assisted support by the pier. Commonly known drawbacks or deficiencies of such foundation lifting collet clamp assemblies arise as the result of the mechanically required orientation of the conical bore of the collet clamp's drawing sleeve, and as the result of the mechanically required annular or completely circumferential configuration of the clamp's drawing sleeve component.
In order for the drawing sleeve component of a pier clamping assembly to effectively radially inwardly drive the assembly's wedge shaped collet shoes against a pier section which extends vertically through the sleeve, such sleeve's conical bore must flare or widen in the downward direction. The direction of the downward flare is necessarily consistent with the downwardly directed forces which are applied by the collet clamp to the pier upon pier driving or upon subsequent foundation lifting. Such mechanically necessary downward flare of the drawing sleeve's conical bore results in a thickening of the annular wall of the drawing sleeve at its upper end, and results in a corresponding thinning of such wall at the sleeve's lower end. In order for such drawing sleeves to effectively drive their wedge shaped collet shoes radially inwardly against the outer wall of a pier to be annularly clamped, the horizontal cross-sectional shape of the drawing sleeve must remain precisely circular, especially at such sleeve's lower end. In the event that the lower end of the drawing sleeve deforms into an oval horizontal cross-sectional shape, the size or “footprint” of the underlying contact points between the teeth of the wedge shaped collet shoes and the pier becomes undesirably diminished and localized along narrow vertically extending lines of contact rather than along the circumferentially extending ridges of the teeth. Such diminishment of contact points reduces friction. Accordingly, upon occurrence of such drawing sleeve wall deformation, slippage of the pier through the clamping assembly may undesirably occur. Where hydraulic cylinder attaching clevises or eyed flanges are directly welded to the outer wall of the drawing sleeve of such collet clamp assembly (a configuration commonly utilized in the foundation lifting arts) downwardly directed load forces applied to such flanges or clevises tend to lever or twist such flanges or clevises against the relatively thin walled lower periphery of the drawing sleeve. Resultant extreme localized twisting forces directed against the relatively thin lower end of the drawing sleeve tends to undesirably bend the drawing sleeve into such oval shape, causing clamp slippage.
A second drawback or deficiency (arising as the result of the completely annular or circumferential configuration of the drawing sleeve component of the collet clamp) becomes especially disadvantageous in circumstances where foundation lifting apparatus must erected within and operated within a vertically restrictive space such as a building's crawl space. Where, for example, a building has a foundation footing extending two feet below ground level and has floor joists overlying ground level by three feet, the vertical distance between the building's floor joists and the undersurface of the foundation footing totals five feet. Such five foot vertical space would typically be recognized as a restricted. Steel pier segments which are initially downwardly driven into the earth from within such a restricted space are necessarily shortened to at least five feet in length. However, the typically completely annular and completely circumferential configuration of the collet clamp assembly typically vertically partitions such five feet of useable vertical work space at a point no lower than the upper ends of the hydraulic cylinders which are utilized for pier driving and foundation jacking. Such vertical partitioning effect imposed within an already restricted vertical space (such as the exemplary five foot installation space) undesirably further limits the lengths of pier sections which may be utilized. The requirement of use of further shortened pier sections within such restricted vertical work space undesirably multiplies pier installation steps, is time consuming, and magnifies the risk that the above ground portion of the vertical string of shortened pier sections will laterally buckle.
The instant inventive assembly for driving pier sections and for foundation lifting solves or ameliorates the drawbacks and deficiencies of commonly known configurations of foundation jacking assemblies noted above by incorporating within such assembly a specially configured “T” bar which transfers deforming torque or twisting forces away from the collet clamp's drawing sleeve and which downwardly move the location of the vertical partition imposed by such drawing sleeve.